ggplot2 geom_boxplot limits

With base graphics, one can use the "ylim" argument to zoom in on a

With ggplot2, using "limits" to try to zoom in on a boxplot *changes the

The toy code below demonstrates this. In ggplot2, "zooming in" causes the

In base graphics, "zooming in" does not cause the boxes to overlap or, as

What is going on here?

pdf(file="toy-example.pdf")
set.seed(1)
toy1<-data.frame(Y=rnorm(500, mean=3), A="one")
toy2<-data.frame(Y=rnorm(500, mean=1.6), A="two")
toy<-rbind(toy1,toy2)
toy$A<-factor(toy$A)
library(ggplot2)
mybreaks<-signif(seq(from=min(toy$Y),to=max(toy$Y),by=0.5),digits=2)
mylimits<-c(0.61,3.7)
print(myplot<-ggplot(toy, aes(x=A,y=Y)) +

print(myplot+scale_y_continuous(breaks=mybreaks,limits=mylimits))
boxplot(toy1$Y,toy2$Y)
boxplot(toy1$Y,toy2$Y, ylim=mylimits)
graphics.off()

sessionInfo()

R version 3.2.1 (2015-06-18)
Platform: x86_64-apple-darwin13.4.0 (64-bit)
Running under: OS X 10.10.4 (Yosemite)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] ggplot2_1.0.1

loaded via a namespace (and not attached):
 [1] MASS_7.3-40      colorspace_1.2-6 scales_0.2.5     magrittr_1.5

 [9] Rcpp_0.11.6      stringi_0.5-5    grid_3.2.1       stringr_1.0.0

Jacob A. Wegelin

Limits in scales set values outside the limits to NA. Hence the boxplots, smoothers,... change. Use coord_cartesian() to "zoom in".

Op 20-jul.-2015 20:29 schreef "Jacob Wegelin" <jacobwegelin at fastmail.fm>:

With base graphics, one can use the "ylim" argument to zoom in on a boxplot.

With ggplot2, using "limits" to try to zoom in on a boxplot *changes the box*.? Since the box usually indicates the 25th and 75th percentiles of a

quantitative variable, this is puzzling.

The toy code below demonstrates this. In ggplot2, "zooming in" causes the two boxes to overlap, when they did not overlap in the full plot.? Also, the

center lines --- which usually indicate the median of the variable --- change when one zooms in.

In base graphics, "zooming in" does not cause the boxes to overlap or, as far as I can see, the median line to move relative to the scale.

What is going on here?

pdf(file="toy-example.pdf")
set.seed(1)
toy1<-data.frame(Y=rnorm(500, mean=3), A="one")
toy2<-data.frame(Y=rnorm(500, mean=1.6), A="two")
toy<-rbind(toy1,toy2)
toy$A<-factor(toy$A)
library(ggplot2)
mybreaks<-signif(seq(from=min(toy$Y),to=max(toy$Y),by=0.5),digits=2)
mylimits<-c(0.61,3.7)
print(myplot<-ggplot(toy, aes(x=A,y=Y)) + geom_boxplot()+scale_y_continuous(breaks=mybreaks)+theme_bw())
print(myplot+scale_y_continuous(breaks=mybreaks,limits=mylimits))
boxplot(toy1$Y,toy2$Y)
boxplot(toy1$Y,toy2$Y, ylim=mylimits)
graphics.off()

sessionInfo()

R version 3.2.1 (2015-06-18)
Platform: x86_64-apple-darwin13.4.0 (64-bit)
Running under: OS X 10.10.4 (Yosemite)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats? ? ?graphics? grDevices utils? ? ?datasets? methods? ?base

other attached packages:
[1] ggplot2_1.0.1

loaded via a namespace (and not attached):
?[1] MASS_7.3-40? ? ? colorspace_1.2-6 scales_0.2.5? ? ?magrittr_1.5? ? ?plyr_1.8.3? ? ? ?tools_3.2.1? ? ? gtable_0.1.2? ? ?reshape2_1.4.1
?[9] Rcpp_0.11.6? ? ? stringi_0.5-5? ? grid_3.2.1? ? ? ?stringr_1.0.0? ? digest_0.6.8? ? ?proto_0.3-10? ? ?munsell_0.4.2


Jacob A. Wegelin

On 2015-07-20 Mon 15:19, Thierry Onkelinx wrote:

Limits in scales set values outside the limits to NA. Hence the boxplots,
smoothers,... change. Use coord_cartesian() to "zoom in".

Thanks. What do I do if I also want to use coord_flip(), that is, if I
want the boxes to lie horizontally *and* to zoom in?

myplot+coord_cartesian(ylim=mylimits) # zooms in

myplot+coord_cartesian(ylim=mylimits) + coord_flip() # flips but does not
zoom

myplot + coord_flip()+coord_cartesian(ylim=mylimits) # zooms but does not
flip

Jacob Wegelin


 Op 20-jul.-2015 20:29 schreef "Jacob Wegelin" <jacobwegelin at fastmail.fm>:

With base graphics, one can use the "ylim" argument to zoom in on a

boxplot.

With ggplot2, using "limits" to try to zoom in on a boxplot *changes

the box*.  Since the box usually indicates the 25th and 75th percentiles of
a
quantitative variable, this is puzzling.

The toy code below demonstrates this. In ggplot2, "zooming in" causes

the two boxes to overlap, when they did not overlap in the full plot.
Also, the
center lines --- which usually indicate the median of the variable ---
change when one zooms in.

In base graphics, "zooming in" does not cause the boxes to overlap or,

as far as I can see, the median line to move relative to the scale.

What is going on here?

pdf(file="toy-example.pdf")
set.seed(1)
toy1<-data.frame(Y=rnorm(500, mean=3), A="one")
toy2<-data.frame(Y=rnorm(500, mean=1.6), A="two")
toy<-rbind(toy1,toy2)
toy$A<-factor(toy$A)
library(ggplot2)
mybreaks<-signif(seq(from=min(toy$Y),to=max(toy$Y),by=0.5),digits=2)
mylimits<-c(0.61,3.7)
print(myplot<-ggplot(toy, aes(x=A,y=Y)) +

geom_boxplot()+scale_y_continuous(breaks=mybreaks)+theme_bw())

print(myplot+scale_y_continuous(breaks=mybreaks,limits=mylimits))
boxplot(toy1$Y,toy2$Y)
boxplot(toy1$Y,toy2$Y, ylim=mylimits)
graphics.off()

sessionInfo()

R version 3.2.1 (2015-06-18)
Platform: x86_64-apple-darwin13.4.0 (64-bit)
Running under: OS X 10.10.4 (Yosemite)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] ggplot2_1.0.1

loaded via a namespace (and not attached):
 [1] MASS_7.3-40      colorspace_1.2-6 scales_0.2.5     magrittr_1.5

 plyr_1.8.3       tools_3.2.1      gtable_0.1.2     reshape2_1.4.1

 [9] Rcpp_0.11.6      stringi_0.5-5    grid_3.2.1       stringr_1.0.0

  digest_0.6.8     proto_0.3-10     munsell_0.4.2

Jacob A. Wegelin